Acta Bot. Croat. 78 (1), 91–94, 2019 CODEN: ABCRA 25 DOI: 10.2478/botcro-2018-0009 ISSN 0365-0588 eISSN 1847-8476

Short communication

A new addition to the alien flora of Tunisia, Amaranthus spinosus L. ( s.l.), with notes on A. diacanthus Raf.

Duilio Iamonico1*, Ridha El Mokni2,3

1 University of Rome Sapienza, Department PDTA, Section Environment and Landscape, via Flaminia 72, 00196 Rome, Italy 2 Laboratory of Botany and Ecology, Faculty of Sciences of Bizerta, University of Carthage, Jarzouna-7021, Bizerta, Tunisia 3 Faculty of Pharmacy of Monastir, University of Monastir, BP. N° 207, Avenue Avicenna, Monastir-5000, Tunisia

Abstract – Amaranthus spinosus L. (Amaranthaceae s.l.), a species native to the Neotropics, has been found in four localities (Bizerta, Bir Bouregba, Hammamet, and Nabeul) of N. Tunisia. Our discovery represents the first record at national level, and the second one for N. Africa. Morphological characters and ecological data are given. Nomencla- tural notes are provided for the name A. diacanthus, which was regarded by some authors as heterotypic synonym of A. spinosus. A neotype is designated in the present paper based on a specimen preserved at LSU. Keywords: alien species, Amaranthus, neophyte, typification

Introduction

The genus Amaranthus L. (Amaranthaceae Juss.) com- Amaranthus spinosus, which is recorded in many countries prises about 70 mostly annual, monoecious and dioecious of central and southern parts of the continent, while in the species, of which approximately 40 are native in America north it occurs only in Egypt. As part of an ongoing no- (see e.g., Costea et al. 2001, Iamonico 2015a). Some species menclatural and taxonomic study on the genus Amaranthus of Amaranthus are used as ornamentals and are able to es- (see e.g., Iamonico 2014a, 2014b, 2015a, 2015c, 2016a, 2016b, cape from cultivation, having an economic impact mainly 2016c, Iamonico and Das 2014) and the Tunisian Amaran- on agricultural systems (reduction of productivity and crop thaceae s. lat. (see e.g., Iamonico and El Mokni 2017, Suk- quality), while other taxa have an ecological impact on native horukov et al. 2016), some populations have been found that flora and vegetation [e.g. A. tuberculatus (Moq.) J.D.Sauer in certainly refer to A. spinosus. The number of TunisianAma - a riparian habitat] (see e.g., Iamonico 2015b). The infrage- ranthus species has thereby been increased, since this find- neric classification of Amaranthus still remains unresolved, ing represents the first record for the Flora of Tunisia and the lacking a comprehensive molecular study (see e.g., Hernán- second for the Flora of N. Africa. Moreover, the name Ama- dez-Ledesma et al. 2015). On the basis of morphology and ranthus diacanthus, which some authors suggest be regard- chorology, Mosyakin and Robertson (1996) recognized three ed as a synonym of A. spinosus (e.g., Rojas-Sandoval 2015, subgenera: subg. Acnida (L.) Aellen ex K.R. Robertson with Wunderlin et al. 2017), is here investigated from the nomen- three sections, subg. Albersia (Kunth) Gren. et Godr. with clatural point of view, as it is still untypified. four sections, and subg. Amaranthus, with three sections and two subsections. According to Mosyakin and Robert- son (1996: 278), Amaranthus spinosus L. is the only species Materials and methods belonging to Amaranthus subg. Amaranthus sect. Centrusa The work is based on an extensive analysis of literature, Griseb. and examination of the specimens kept in the Herbaria FI, The Flora of Africa (see SANBI 2012 and literature there- HFLA, LINN, LSU, and RO (acronyms according to Thiers in, Iamonico 2015c and literature therein) currently includes 2019+), and in the Herbarium of the Faculty of Pharmacy of

* Corresponding author, e-mail: [email protected]

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Monastir and of the Faculty of Sciences of Bizerta (not listed 0.3 km NW of Richardson Cemetery, 14 July 2003, L. Blay, T. in Index Herbariorum), where the personal collections of R. Pazzaglia et N. Hastings 906 (LSU-83081!). Image of the neo- El Mokni are kept. type available at http://data.cyberfloralouisiana.com/lsu/). The articles cited through the text agree with the Shenzen Description – Herbs 6–15 dm tall, monoecious, annual Code, ICN (Turland et al. 2018). (therophyte). Stems erect, glabrous brownish, branched. Le- aves green to reddish (on the upper surface), ovate to lanceo- late, rhomboidal [(2.0–)2.5–6.5(–7.5) × (1.0–)2.5–4.0(–3.5) Results and discussion cm], with entire margins, apex obtuse or acute, mucronate, Nomenclatural notes on Amaranthus diacanthus base cuneate, glabrous, petioled (petiole 1.5–8.5 cm long), Rafinesque (1817: 31–32) described A. diacanthus and associated to 2 spine-like structures (modified ), 7.0– provided a short diagnosis. Rafinesque (l.c.) also cited the 8.0 mm long. Synflorescences terminal, panicle-like, the main florescence up to 15 cm long, usually green and axillary Flore Louisinaise by Robin (1807). The latter author (Robin glomerules. Floral bracts lanceolate (3.0–4.0 × 0.5−1.0 mm) 1807: 372) listed an Atriplex taxon, but he did not report any as long as or shorter than the perianth, acute, awned, mar- epithet. As a consequence, Rafinesque (l.c.), probably on the gin entire, glabrous. Staminate flowers with 5 tepals, ovate- basis of the detailed description made by Robin (l.c.), pro- lanceolate; stamens 5. Pistillate flowers with 5 tepals, lanceo- posed the occurring in Louisiana (S-USA) as a new late–spathulate (3.5–4.0 × 0.9–1.0 mm), with usually obtuse species. We have not been able to trace Rafinesque’s materi- and mucronate apex; stigmas 3–4. Fruit brown or yellow- al, which could be useful for typification purposes. We loo- ish, ellipsoidal (2.0–2.1 × 1.4–1.5 mm) as long as or slightly ked at material collected by C. C. Robin in Louisiana, which shorter than the perianth, smooth below, rugose on top, de- could be observed and used by C. S. Rafinesque, to describe hiscent. Seed lenticular (about 0.9 mm in diameter), brown. A. diacanthus. Unfortunately, no Robin specimen was traced Phenology – Flowering and fruiting time October-De- [moreover, Stafleu and Cowan (1985: 812) reported “Herba- cember. rium and Types: Unknown”]. Since no original material se- ems to be extant, no lectotype can be designed, and neotypi- Habitat – Roadsides, public gardens, and cultivated areas fication is required (see Arts. 9.2, 9.3, and 9.7). Accordingly, with trees (e.g. Citrus sp.), at 6–41 m a.s.l. we selected a specimen preserved at LSU (catalog number 83081) and collected in Louisiana, in Webster County. The LSU-83081 is here designated as the neotype of the name Amaranthus diacanthus. Concerning the identity of A. diacanthus, note that the diagnosis by Rafinesque (1817) and the description of Atriplex sp. made by Robin (1807) include an important morphological character [“...glomerulis bispinosis...” by Ra- finesque (1807), and “...les paques de fleurs des sisselles -ac compagnés de deux épines divergentes...” by Robin (1807)]: the occurrence of a spine-like feature at the bases of the flo- ral glomerules [according to Costea and Tardif (2003) the- se structures are actually the bracts of the first flower in the first cyme of the glomerule which metamorphoses in the ear- ly phase of the onthogeny]. This structure was the basis for the selection of the neotype, representing a unique feature in the genus Amaranthus, characterizing the species currently known as A. spinosus (see e.g., Bojian et al. 2003, Mosyakin and Robertson 2003, Iamonico 2015a). As a consequence, these two names can be treated as heterotypic synonyms, the Linnaean having nomenclatural priority (1753 vs. 1817).

Taxonomic treatment Amaranthus spinosus L., Sp. Pl., 2: 991. 1753. Lectotype (designated by Fawcett and Redle 1914: 103): Herb. Linnaeus, no. 1117.27 (LINN!). Image of the lectotype available at http://linnean-online.org/11653/). = Amaranthus diacanthus Raf., Fl. Ludov.: 31-32. 1817. Fig. 1. Habit of Amaranthus spinosus L. (bar = 1 cm) at Nabeul Neotype (here designated): U.S.A., Louisiana, Webster region in Tunisia with detail of spine-like structures (left corner; County, Camp Minden, 1.2 km E of Jim Davis Cemetery, bar = 4 mm) (photos by R. El Mokni).

92 ACTA BOT. CROAT. 78 (1), 2019 AMARANTHUS SPINOSUS IN TUNISIA

Distribution in Tunisia – Four populations (16-18 in- Chromosome number – A. spinosus is a diploid species dividuals in total) were found in the following localities: with 2n = 34 (see e.g., Greizerstein and Poggio 1992, Song et Bizerta [three individuals (each about 150 cm tall) cover- al. 2002, Sheidai and Mohammadzdeh 2008). ing an area of 9 m2], Bir Bouregba [two individuals (each Specimina visa – Tunisia: Bizerta (North-Bizerta, Cor- about 70 cm tall) covering 2 m2], Hammamet [three-four niche), 37°19'31" N, 09°51'52" E, uncultivated land, 06 m individuals (each about 90 cm tall covering 4 m2], and Na- a.s.l., 27 October 2013, R. El Mokni (HFLA, Herb. Univ. beul [eight-nine individuals (each about 60 cm tall) cov- Bizerta); Nabeul (North-Nabeul, Cap-Bon), 36°26'26" N, ering 25 m2]. 10°42'25" E, roadsides, 08 m a.s.l., 09 December 2015, R. Native range and status of naturalization in Tunisia – A. El Mokni (Herb. Univ. Monastir); Nabeul (North-Hamma- spinosus is a neophyte species native to the Neotropics, while met, Cap-Bon), 36°24'35" N, 10°36'06" E, cultivated land, it is an alien in many countries of Europe (Iamonico 2015c), 22 m a.s.l., 10 December 2016, R. El Mokni (Herb. Univ. C. and S. Africa (Sanbi 2012), N. and E. Australia (Atlas Liv- Monastir); Nabeul (Bir Bouregba, Cap-Bon), 36°25´39" N, ing of Australia 2016), and Asia (see e.g., Townsend 1974, 10°34'56" E, roadsides, 41 m a.s.l., 09 December 2015, R. El Bojian et al. 2003). Concerning N. Africa, this species was Mokni (Herb. Univ. Monastir). previously recorded only in Egypt (see Boulos 2009: 56, Ia- monico 2015c). Acknowledgements The four populations of A. spinosus discovered in Tuni- sia (see above “Distribution in Tunisia”) were observed from Thanks to the Directors and Curators of all quoted of- 2012 to 2016. Although the plants seem to self-replace with- ficial herbaria and colleagues who own the cited personal out direct human intervention, we prefer to consider A. spi- herbaria for their support during our visits, loan of speci- nosus as casual alien species in Tunisia at the moment. mens, photographs or for providing interesting information.

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